When optical fibres and/or electrical conductors are required to pass through a bulkhead separating a high pressure environment from a low pressure environment, for example up to 15000 psi (104 MN.m.sup.-2 ) on the high pressure side and atmospheric or near atmospheric pressure on the low pressure side, high axial loads are generated in the fibres and conductors.
A particularly difficult environment exists for a submarine telecommunications system in which the transmission of information is accomplished with a transmission cable and amplifiers at spaced apart locations along the cable to amplify the information signals, thus compensating for the loss caused by the cable. Such an amplifier is housed in a strong watertight housing and a bulkhead seals each end of the housing. The cable passes through a gland in this bulkhead and the gland forms a watertight seal between the cable and the bulkhead.
With conventional submarine telecommunication systems utilising polythene sheathed coaxial electric cables, the sealing of the cable to the bulkhead has been achieved by providing on the bulkhead an integral hollow castellated spigot, passing the cable through the hollow spigot and the bulkhead and moulding polyethylene around the spigot and the cable sheath. The dielectric between the inner and outer conductor of the coaxial cable is formed of solid low-loss polythene, and in the event of a cable break adjacent the repeater, caused for example by a dragged ship anchor, the chance of water passing along the inside of the broken cable into the repeater is remote.